body {
    padding: 0;
    margin: 0;
    overflow: hidden;
    height: 600px;
}

canvas {
    padding: 0;
    margin: 0;
}

div.btnbg {
    position: fixed;
    left: 0;
    top: 0;
}

img.logo {
    position: absolute;
    left: 50%;
    top: 50%;
    transform: translate(-50%, -50%);
    max-width: 320px;
}